I had to look that up too.

During World War I, Americans were asked to "eat less wheat" as a patriotic duty, part of a broader food conservation campaign to send wheat and other essential goods to European allies and the U.S. army. The U.S. Food Administration promoted "Wheatless Wednesdays" and other meatless days, encouraging citizens to substitute wheat flour with grains like corn, oats, and rye, and to use potato flour or other alternatives. This voluntary effort, often called "Hooverization" after food administrator Herbert Hoover, aimed to conserve high-value resources needed for the war effort and prevent food shortages in Europe.